1. Field of the Invention
The present invention relates to a resist for a fine pattern forming technique, a resist process technique and an exposing method. More particularly, the present invention relates to a technique mainly employed for a system for transferring a fine pattern formed on a mask by an X-ray proximity exposure technique in a technique of transferring a fine pattern for fabricating a semiconductor integrated circuit, for enabling transfer of a finer pattern at a higher speed than the prior art.
2. Description of the Background Art
FIG. 1 shows representative results of the relation between resolution and exposure wavelengths in X-ray proximity exposure. Referring to FIG. 1, the horizontal axis shows the exposure wavelengths (xc3x85), and the vertical axis shows the resolution (nm). It has been regarded that the resolution in X-ray proximity exposure is decided by two different factors, i.e., the resolution limit of an optical image decided by Fresnel diffraction and the resolution limit decided by blurring resulting from the so-called secondary electrons, i.e., pattern blurring (reduction of resolution: hereinafter simply referred to as blurring) resulting from sensitization of a resist with photoelectrons and Auger electrons generated in the resist irradiated with exposure light.
The resolution limit R resulting from Fresnel diffraction is expressed as follows:
R=kxc2x7(xcexxc2x7D)1/2
where k represents a constant, xcex represents the exposure wavelength, and D represents the distance between a mask and a wafer. It is understood from the above equation that the resolution is increased as the exposure wavelength as well as the distance between the mask and the wafer are reduced.
On the other hand, blurring caused by secondary electrons generated in the resist irradiated with X-rays is proportionate substantially to the 1.75th power of X-ray energy of the exposure wavelength. It has been regarded that the so-called ground range (=46/"sgr"xc3x97E1.75, where "sgr" represents the density (gxc2x7cm3) of the resist and E represents the energy (KeV) of electrons) of the secondary electrons in the resist decides the resolution.
However, it has recently been clarified by more detailed experimental study and theoretical study that blurring of electrons is smaller than the ground range and the resolution limit resulting from the blurring of electrons moves toward a short-wave side. According to this clarification, it follows that the optimum wavelength for obtaining a pattern of high resolution can be newly reduced from the conventional level of 7 xc3x85 to 6 xc3x85 in the case of 10 xcexcm gap. However, it has been understood that the actual resolution limit is decided not only by Fresnel diffraction but also by blurring resulting from secondary electrons. In other words, the curves shown in FIG. 1 are plotted on the assumption that the actual resolution is decided by the average sum of squares of the two resolution limits deciding the resolution. According to FIG. 1, it follows that the resolution cannot be much increased by reducing the exposure wavelength, and hence short-wave exposure has not been studied.
The present invention has been proposed on the basis of recognition obtained by making detailed study in relation to blurring resulting from secondary electrons such as photoelectrons and considering conditions for increasing resolution by reducing the exposure wavelength. The present invention relates to a technique of spreading the limit of application of the X-ray proximity exposure technique to a fine region for transferring a pattern of high resolution at a high speed. Thus, the present invention aims at solving a problem caused in a technique for improving resolution by reducing the resolution limit resulting from Fresnel diffraction by employing X-rays having a shorter wavelength than that studied in the conventional X-ray proximity exposure technique for exposure.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.